In oblique-track tape decks, it is necessary that the recorded track be laid down precisely on the magnetic tape, so that magnetic tapes played on various machines of the same system provide the same reproduction. One criterion for this is the distance of video tracks from an edge of the tape used as a reference edge. For precise adjustment of this distance, the head wheel height must be adjustable to within precise tolerances upon initial assembly and upon every replacement of the head wheel.
SCHULEIN/GRUNDIG (German Patent Disclosure Document DE-OS 31 30 801) discloses how to avoid tedious mechanical adjustment of the head wheel height by electrical adjustment, namely adjusting the phase difference between head wheel tachometer pulses and specified image pulses. This method has, however, the disadvantage that, due to the possible shifting of the sampling interval in the circumferential direction of the sampling or scanning device, the mechanical looping of the magnetic tape about the sampling device must be chosen greater than is theoretically necessary. This results in the storage surface on the magnetic tape being generally poorly used.
TAKAHASHI/JVC (U.S. Pat. No. 4,564,876 and German Patent Disclosure Document DE-OS 32 44 215) discloses how to axially slide the head wheel of a rotating magnetic head device to facilitate proper tracking. However, this relates to the shifting of the head wheel in operation, and not to the precise adjustment of the head wheel height in initial or starting condition. Furthermore, in conventional rotating magnetic head devices, the biassing pressure on or among the ball bearings changes, in correspondence with the axial position of the head wheel.